Problem: Michael starts counting at 30, and he counts by fives. If 30 is the 1st number that Michael counts. what is the 15th number that he counts?
Answer: What is the first number that he counts? $30$ What is the second number that he counts? $\begin{align*}&30 + 5 \\ &= 35\end{align*}$ What is the third number that he counts? $\begin{align*}&30 + 5 + 5 \\ &= 30 + (2 \times 5) \\ &= 40\end{align*}$ What is the 15th number that he counts? $\begin{align*}&30 + (14\times5) \\ &= 30 + 70 \\ &= 100\end{align*}$